The present invention relates generally to alarm valves and double check valve arrangements and more particularly relates to alarm valves and double check valve arrangements for use in fire suppression, water sprinkler systems.
A typical fire suppression water sprinkler system as installed in many buildings includes an array of individual fire sprinklers which are supplied with water through a main conduit and various branch conduits. The individual fire sprinklers are generally provided with a member that melts when the ambient temperature reaches a predetermined level indicative of a fire. The melting of the member opens the fire sprinkler to spray water in order to suppress the fire. The individual fire sprinklers are provided with meltable members so that the spray of water will hopefully be limited to the region of the building where the fire is present. In this way, the extent of water damage may be minimized.
Such fire suppression systems also oftentimes have one or more alarms that detects the flow of water through the main conduit and through branch conduits to indicate that a fire has started. The alarm typically triggers an audible signal to warn occupants of the building that a fire has started and may also send an appropriate signal directly to a fire department.
Especially in multi-floor sprinkler systems, a waterflow indicator alarm is typically provided for each floor or main branch of the main water supply conduit. The waterflow indicators generally include a member which extends into the passageway of the conduit. A flow of water, even from a single sprinkler is sufficient to move the member and trigger the alarm. Oftentimes, such waterflow indicator alarms are electrically connected to an audible alarm signal generator as well as to light panels to indicate the area in which the fire has occurred.
Another type of alarm is conventionally provided by an alarm valve that is provided in the main conduit. The alarm valve is constructed essentially as a check valve and includes a valve member or clapper that is normally held closed by static line pressure or by a spring such as when all of the individual sprinklers are closed. When one or more sprinklers opens, for example, due to a fire, the clapper provided in the alarm valve lifts off of its seat and an alarm is sounded.
Typically, when the clapper in the alarm valve lifts off of its seat, water under pressure is permitted to flow into a retarding chamber. The retarding chamber prevents false alarms due to surges or minor water pressure fluctuations. When the flow from the alarm valve into the retarding chamber is sufficient, the water drives a motor to sound an alarm. In addition, the flow of enough water into the retarding chamber may trigger an electrical alarm as a redundancy. The alarm may also be triggered electrically in response to a sensing of a flow of water through the valve (typically, a riser check valve) by a paddle switch. In this arrangement, the alarm is generally electrically operated rather than mechanically operated.
Fire suppression systems which include water sprinklers are oftentimes in fluid communication with the community water supply system or with whatever source of potable water is available in the vicinity. The water within the fire suppression system itself, however, can remain within the piping for a considerable period of time and is considered to be stagnant water. In addition, sometimes a pumper provided by the fire department will be connected to an inlet in communication with the fire suppression system in order to provide additional water and/or pressure in the event of a fire. The pumper may be in turn in communication with a source of non-potable water which could potentially enter the potable water supply in a backflow condition. Accordingly, it is desirable, and frequently required by ordinance that a backflow prevention device be provided between the arrangement of sprinklers and the water main conduit.
Most often, the backflow prevention is provided by a pair of spring loaded check valves that are located upstream of the alarm valve and at the connection of the fire suppression system to the potable water supply. Two check valves are required in order to provide an assurance that there will not be a backflow of stagnant water into the potable water supply. Frequently, the use of two check valves in the backflow prevention device is also required by ordinance.
In use, the two check valves are arranged so that both check valves are spring loaded in a closed configuration under normal pressure conditions. However, each check valve results in a pressure drop in the main conduit across the check valve. For example, if the main conduit has a supply pressure of 60 psi, there will be a pressure drop of perhaps 6 psi due to the first check valve. Accordingly, the pressure downstream of the first check valve may be 54 psi. The second check valve will also provide a pressure drop of perhaps 3 psi resulting in a pressure of 51 psi downstream of the second check valve. If all of the sprinklers remain closed and the supply pressure is maintained, the first and second check valves will remain closed.
If one or more of the sprinklers should open, the first and second check valves will both open to enable water to be supplied to the arrangement of sprinklers.
In the event that the supply pressure should drop below the pressure downstream of the second check valve, the first and second check valves are arranged to remain closed (or will close if they should happen to be open due to one or more of the sprinklers having opened). The second check valve will prevent the water in the piping downstream of the second check valve from flowing back through the second check valve. Likewise, the first check valve will provide a redundant protection against a backflow of the stagnant water into the main supply conduit.
Sometimes, however, one or both of the check valves may be fouled and remain open when they should be closed. If at least one of the check valves should not be fouled and closes normally, a backflow of stagnant water into the potable water supply would be prevented.
In the event that both check valves should become fouled, however, the passageway between the first and second check valves can be provided with a hydraulically actuated relief valve and a vacuum breaker valve that together form a reduced pressure zone in the passageway. Under normal conditions, both the hydraulically actuated relief valve and the air/vacuum valve are closed. However, if both of the check valves should fail, the water which flows back through the second check valve is drained out of the system through the hydraulically actuated relief valve. This relief valve opens whenever the supply pressure (e.g. 60 psi) in the main conduit upstream of the first check valve is not sufficiently greater (typically about a 2 psi differential is required) than the pressure in the passageway between the two check valves.
The air/vacuum valve also opens whenever there is zero pressure or a negative pressure in the passageway between the two check valves. In this way, air is permitted to enter the main conduit through the first check valve and a siphonage of stagnant water is prevented.
To provide a separate alarm valve and a pair of check valves as a backflow prevention device typically requires that three separate check valves and three associated OS&Y gate valves (one on each side of the first two check valves and one upstream of the alarm valve or "third check valve" which is oftentimes remote from the first two check valves) be provided in the main water supply conduit. In the present invention, the need for two of the OS&Y gate valves and one of the check valves is eliminated. The two OS&Y gate valves can be eliminated because according to the present invention, one OS&Y gate valve performs the task of isolating the backflow preventer for testing and also the task of isolating the alarm valve and downstream system for service and resetting, if necessary. The OS&Y valve downstream of the backflow preventer is used only to create a static condition for testing and can be eliminated in the arrangement of the present invention because a water sprinkler system (i.e., the alarm valve and the closed system provided by the arrangement of sprinkler valves and associated piping) is static in its normal mode.
The use of three OS&Y gate valves and three check valves involves the expenditure of considerable time and expense during the installation of such plumbing. In addition, the use of three separate check valves results in a supply pressure which has been significantly decreased due to the pressure drop which occurs across each check valve. As a result the flow of water to the arrangement of water sprinklers may be inadequate, or a costly supplemental pumping arrangement may be required to supply all of the sprinklers needed for the fire suppression system, or a compensating increase in pipe size may be required to accommodate the reduced flow caused by the extra check valve.
In addition, it is conventional to provide an arrangement for detecting the flow of water through the backflow preventer to detect leaks and to provide a detection point for unauthorized use of water such as in an illegal tap into the fire protection system. A typical, known arrangement is disclosed by the Watts Regulator Company of Andover Mass. as the double detector reduced pressure check valve/backflow preventer (Series 909DDC). Such an arrangement, however, is itself costly to manufacture and to install and necessitates that the bypass piping be provided with backflow prevention in addition to the backflow prevention necessary for the main line of the fire protection system.
Accordingly, it is an object of the present invention to provide a combined alarm and backflow prevention check valve arrangement for a fire suppression water sprinkler system which overcomes the disadvantages of the prior art.
Yet another object of the present invention is to provide a combined alarm and backflow prevention arrangement which is efficient and economical by minimizing the number of check valves and OS&Y gate valves which are required in the system.
Another object of the present invention is to eliminate two OS&Y gate valves which are normally installed upstream and downstream of a standard design double check valve, reduced pressure zone, backflow prevention device to provide a static condition for testing the backflow prevention device.
Still another object of the present invention is to provide a combined alarm and backflow prevention arrangement for a fire suppression system which minimizes the total pressure drop in the system due to the use of check valves.
Yet still another object of the present invention is to provide a plumbing fitting which is adapted to connect a check valve and an alarm valve together so as to provide a combined alarm and backflow prevention arrangement which overcomes the disadvantages of the prior art.
Still another object of the present invention is to provide an arrangement for detecting leaks and possibly illegal use of water in a backflow preventer which overcomes the disadvantages of the prior art.
These and other objects are accomplished by a combined alarm and backflow prevention arrangement for a fire suppression sprinkler system, having a main conduit and an arrangement of individual sprinklers downstream of the main conduit. The combined alarm and backflow prevention arrangement includes a first check valve which is provided in the main conduit upstream of the arrangement of individual sprinklers and an alarm valve formed by a second check valve which is provided in the main conduit downstream of the first check valve and upstream of the arrangement of individual sprinklers. An alarm is provided to indicate when the alarm valve is open. Fluid communication is provided between the first check valve and the alarm valve and, in a preferred embodiment, a relief valve is arranged to provide a drain in response to the hydraulic pressure in the main conduit of the fire suppression system. The alarm and backflow prevention arrangement includes only two check valves which are provided in the main conduit.
In another preferred embodiment of the present invention, a plumbing fitting for use in a fire suppression system is provided to connect a check valve and an alarm valve to one another to provide a double check valve backflow preventer and an alarm valve arrangement. The plumbing fitting includes a conduit adapted to couple the plumbing fitting to the check valve upstream of the plumbing fitting and to couple the plumbing fitting to the alarm valve downstream of the plumbing fitting. A drain is provided for draining the plumbing fitting in response to the hydraulic pressure in the main conduit of the fire suppression system.
In another preferred embodiment of the present invention, a combined alarm and backflow prevention arrangement for a fire suppression, water sprinkler system, having a main conduit and an arrangement of individual water sprinklers downstream of the main conduit, includes a first check valve provided in the main conduit upstream of the arrangement of individual sprinklers. An alarm valve including a second check valve is provided in the main conduit downstream of the first check valve and upstream of the arrangement of individual sprinklers. An alarm is provided to indicate when the alarm valve is open. A passageway provides fluid communication between the first check valve and the alarm valve with a valve providing communication between the passageway and the atmosphere when the hydraulic pressure in the passageway falls or becomes zero or negative or falls below a first predetermined amount. A relief valve is provided for draining the passageway in response to the hydraulic pressure in the main conduit of the fire suppression system.
Further preferred embodiments of the present invention employ either a single straight-way stop-check valve or a single angle stop-check valve with the hydraulically actuated relief valve to further reduce the number of parts which are necessary.
In another embodiment of the present invention, a backflow preventer is provided with an impeller flow sensor to detect leaks and possible unauthorized use of water without the need for bypass piping and an additional backflow preventer for the bypass piping.